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K Ramesh - One of the best experts on this subject based on the ideXlab platform.
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analysis of contact zones from whole field isochromatics using reflection Photoelasticity
Optics and Lasers in Engineering, 2018Co-Authors: M P Hariprasad, K RameshAbstract:Abstract This paper discusses the method for evaluating the unknown contact parameters by post processing the whole field fringe order data obtained from reflection Photoelasticity in a nonlinear least squares sense. Recent developments in Twelve Fringe Photoelasticity (TFP) for fringe order evaluation from single isochromatics is utilized for the whole field fringe order evaluation. One of the issues in using TFP for reflection Photoelasticity is the smudging of isochromatic data at the contact zone. This leads to error in identifying the origin of contact, which is successfully addressed by implementing a semi-automatic contact point refinement algorithm. The methodologies are initially verified for benchmark problems and demonstrated for two application problems of turbine blade and sheet pile contacting interfaces.
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scanning schemes in white light Photoelasticity part i critical assessment of existing schemes
Optics and Lasers in Engineering, 2017Co-Authors: Vivek Ramakrishnan, K RameshAbstract:Abstract The use of white light based Three Fringe Photoelasticity (TFP)/RGB Photoelasticity has gained importance in the recent years. With recent advances in TFP, it is possible to resolve fringe orders upto twelve. The main advantage of this technique is that it requires only a single image for isochromatic demodulation, which makes it suitable especially for problems where recording multiple images is difficult. The accuracy of isochromatic data obtained using TFP/RGB Photoelasticity is dependent on the scanning scheme used to refine the data, which is necessary to incorporate fringe order continuity. In this paper, the existing scanning schemes are critically evaluated for their ability to scan the entire model domain, influence of seed point selection and noise propagation. The scanning schemes are assessed using four problems of increasing level of geometric complexity – Circular disc under compression (simply connected), bi-axially loaded cruciform specimen with an inclined crack, a thick ring subjected to internal pressure and a finite plate with a hole (multiply connected).
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digital Photoelasticity of glass a comprehensive review
Optics and Lasers in Engineering, 2016Co-Authors: K Ramesh, Vivek RamakrishnanAbstract:Abstract The recent advances in digital Photoelasticity have made it possible to use it conveniently for the stress analysis of articles and components made of glass. Depending on the application, the retardation levels to be measured range from a few nanometres to several thousand nanometres, which necessitates different techniques and associated equipments. This paper reviews the recent advances in the Photoelasticity of glass with a focus on the techniques/methods developed in the last decade. A brief introduction to the residual stress in glass is provided initially to bring out its tensorial nature. The subsequent sections are organised thematically rather than chronologically, for better readability and easy access of information.
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a novel method for the evaluation of stress optic coefficient of commercial float glass
Measurement, 2016Co-Authors: Vivek Ramakrishnan, K RameshAbstract:Abstract The measurement of residual stress in float glass is important in glass industries as they affect their cutting quality. Photoelasticity can be used for residual stress analysis of float glass as they exhibit stress induced birefringence. Stress measurement using Photoelasticity necessitates the knowledge of the stress-optic coefficient of float glass. Carrier fringe method in conjunction with digital Photoelasticity is used for the photoelastic calibration of float glass. The conventional method of photoelastic calibration is improved to calibrate float glass with residual stress which eliminates the need for annealing them. The new method developed is self consistent as the results are verified by the reconstruction of the composite fringe pattern. The use of the improved method is recommended for calibration of float glass as it takes into account the residual stress in glass sample apart from its potential for automation.
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residual stress analysis of commercial float glass using digital Photoelasticity
International Journal of Applied Glass Science, 2015Co-Authors: R Vivek, K RameshAbstract:Residual stresses are generated in float glass at the time of manufacturing due to thermal gradients created during the cooling process. The quantification of these residual stresses is important in glass industries as they affect their cutting quality. Photoelasticity can be used for residual stress analysis of glasses, as glass exhibits stress-induced birefringence. In this study, a methodology involving carrier fringes in conjunction with digital Photoelasticity is used to quantify the residual stress in float glass. The results are verified by six-step phase-shifting technique (a subset of ten-step phase-shifting method) using an automatic polariscope. Finally, to demonstrate the utility of the proposed method, the residual stress is measured in float glasses of different thicknesses. A method for approximate estimation of residual stress which does not require sophisticated digital image acquisition and processing systems is also reported.
Michele Scafidi - One of the best experts on this subject based on the ideXlab platform.
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review of rgb Photoelasticity
Optics and Lasers in Engineering, 2015Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:Abstract Automatic methods of Photoelasticity have had a significant progress with the development of automatic acquisition and image processing methods. This article concerns RGB Photoelasticity, which allows the determination of the photoelastic retardation using, usually, a single acquisition of the isochromatic fringes in white light by a colour camera. In particular, the article presents an overview of the main characteristics of RGB Photoelasticity that is influence of the quarter-wave plate error, number of acquisitions, type of light source, determination of low and high fringe orders, methods for searching the retardation, scanning procedures, calibration on a material different from that under test, combined use of the RGB and phase shifting methods. A short section on the applications of RGB Photoelasticity completes the article.
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rgb Photoelasticity applied to the analysis of membrane residual stress in glass
Measurement Science and Technology, 2012Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:The measurement of residual stresses is of great relevance in the glass industry. The analysis of residual stress in glass is usually made by photoelastic methods because glass is a photoelastic material. This paper considers the determination of membrane residual stresses in glass plates by automatic digital Photoelasticity in white light (RGB Photoelasticity). The proposed method is applied to the analysis of membrane residual stresses in some tempered glass. The proposed method can effectively replace manual methods based on the use of white light, which are currently provided by some technical standards.
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rgb Photoelasticity review and improvements
Strain, 2010Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:: This paper considers the main developments of RGB Photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe orders while the fluorescent lamp makes it possible to determine higher fringe orders (12 fringe orders in this paper) owing to the discrete spectrum of the source. The paper shows that, by using the incandescent lamp, the primary limiting factor is the lack of modulation of the R, G and B signals whereas, by using the fluorescent lamp, the limitation of the maximum fringe order derives mainly from the gradient of the fringes and the procedure of search of the retardation.
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phase shifting Photoelasticity in white light
Optics and Lasers in Engineering, 2007Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:The availability of image acquisition systems has led to the development of digital Photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB Photoelasticity and phase shifting Photoelasticity. Phase shifting Photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting Photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.
Augusto Ajovalasit - One of the best experts on this subject based on the ideXlab platform.
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review of rgb Photoelasticity
Optics and Lasers in Engineering, 2015Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:Abstract Automatic methods of Photoelasticity have had a significant progress with the development of automatic acquisition and image processing methods. This article concerns RGB Photoelasticity, which allows the determination of the photoelastic retardation using, usually, a single acquisition of the isochromatic fringes in white light by a colour camera. In particular, the article presents an overview of the main characteristics of RGB Photoelasticity that is influence of the quarter-wave plate error, number of acquisitions, type of light source, determination of low and high fringe orders, methods for searching the retardation, scanning procedures, calibration on a material different from that under test, combined use of the RGB and phase shifting methods. A short section on the applications of RGB Photoelasticity completes the article.
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rgb Photoelasticity applied to the analysis of membrane residual stress in glass
Measurement Science and Technology, 2012Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:The measurement of residual stresses is of great relevance in the glass industry. The analysis of residual stress in glass is usually made by photoelastic methods because glass is a photoelastic material. This paper considers the determination of membrane residual stresses in glass plates by automatic digital Photoelasticity in white light (RGB Photoelasticity). The proposed method is applied to the analysis of membrane residual stresses in some tempered glass. The proposed method can effectively replace manual methods based on the use of white light, which are currently provided by some technical standards.
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rgb Photoelasticity review and improvements
Strain, 2010Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:: This paper considers the main developments of RGB Photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe orders while the fluorescent lamp makes it possible to determine higher fringe orders (12 fringe orders in this paper) owing to the discrete spectrum of the source. The paper shows that, by using the incandescent lamp, the primary limiting factor is the lack of modulation of the R, G and B signals whereas, by using the fluorescent lamp, the limitation of the maximum fringe order derives mainly from the gradient of the fringes and the procedure of search of the retardation.
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phase shifting Photoelasticity in white light
Optics and Lasers in Engineering, 2007Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:The availability of image acquisition systems has led to the development of digital Photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB Photoelasticity and phase shifting Photoelasticity. Phase shifting Photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting Photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.
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towards rgb Photoelasticity full field automated Photoelasticity in white light
Experimental Mechanics, 1995Co-Authors: Augusto Ajovalasit, Sandro Barone, Giovanni PetrucciAbstract:In this paper a new full-field method for the automatic analysis of isochromatic fringes in white light is presented. The method, named RGB Photoelasticity, eliminates the typical drawbacks of the classical approach to Photoelasticity in white light which requires a subjective analysis of colors and an experienced analyst to acquire and interpret the results.
Giovanni Petrucci - One of the best experts on this subject based on the ideXlab platform.
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review of rgb Photoelasticity
Optics and Lasers in Engineering, 2015Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:Abstract Automatic methods of Photoelasticity have had a significant progress with the development of automatic acquisition and image processing methods. This article concerns RGB Photoelasticity, which allows the determination of the photoelastic retardation using, usually, a single acquisition of the isochromatic fringes in white light by a colour camera. In particular, the article presents an overview of the main characteristics of RGB Photoelasticity that is influence of the quarter-wave plate error, number of acquisitions, type of light source, determination of low and high fringe orders, methods for searching the retardation, scanning procedures, calibration on a material different from that under test, combined use of the RGB and phase shifting methods. A short section on the applications of RGB Photoelasticity completes the article.
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rgb Photoelasticity applied to the analysis of membrane residual stress in glass
Measurement Science and Technology, 2012Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:The measurement of residual stresses is of great relevance in the glass industry. The analysis of residual stress in glass is usually made by photoelastic methods because glass is a photoelastic material. This paper considers the determination of membrane residual stresses in glass plates by automatic digital Photoelasticity in white light (RGB Photoelasticity). The proposed method is applied to the analysis of membrane residual stresses in some tempered glass. The proposed method can effectively replace manual methods based on the use of white light, which are currently provided by some technical standards.
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rgb Photoelasticity review and improvements
Strain, 2010Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:: This paper considers the main developments of RGB Photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe orders while the fluorescent lamp makes it possible to determine higher fringe orders (12 fringe orders in this paper) owing to the discrete spectrum of the source. The paper shows that, by using the incandescent lamp, the primary limiting factor is the lack of modulation of the R, G and B signals whereas, by using the fluorescent lamp, the limitation of the maximum fringe order derives mainly from the gradient of the fringes and the procedure of search of the retardation.
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Automated Stress Separation Along Stress Trajectories
Experimental Mechanics, 2007Co-Authors: Giovanni Petrucci, Gaetano RestivoAbstract:A procedure for the separation of principal stresses in automated Photoelasticity is presented. It is based on the integration of indefinite equations of equilibrium along stress trajectories, also known as Lamè–Maxwell equations. A new algorithm for precise and reliable stress trajectory calculation, which is an essential feature of the procedure, has also been developed. Automated stress separation is carried out along stress trajectories starting from free boundaries. Experimental tests were performed on a disc in diametral compression and on a ring with internally applied pressure. Full-field principal stress values were obtained and results were compared with those from the theory of elasticity and with those obtained from the classical shear difference method. It was shown that the proposed method is more accurate and less affected by the presence of residual stresses or experimental errors at the boundaries than the shear difference method. In addition, the method requires little human interaction and is therefore well-suited for automated Photoelasticity.
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phase shifting Photoelasticity in white light
Optics and Lasers in Engineering, 2007Co-Authors: Augusto Ajovalasit, Giovanni Petrucci, Michele ScafidiAbstract:The availability of image acquisition systems has led to the development of digital Photoelasticity both in monochromatic and white light. In particular white light has been used mainly with the following methods: Spectral Content Analysis, RGB Photoelasticity and phase shifting Photoelasticity. Phase shifting Photoelasticity in the colour domain has been used effectively for the determination of the isoclinic parameter in order to reduce the influence of the isochromatic fringes. The method has been also proposed for the determination of the isochromatic fringe order. This paper concerns the general characteristics of phase shifting Photoelasticity in the colour domain. Special attention is drawn towards the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.
Vivek Ramakrishnan - One of the best experts on this subject based on the ideXlab platform.
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scanning schemes in white light Photoelasticity part i critical assessment of existing schemes
Optics and Lasers in Engineering, 2017Co-Authors: Vivek Ramakrishnan, K RameshAbstract:Abstract The use of white light based Three Fringe Photoelasticity (TFP)/RGB Photoelasticity has gained importance in the recent years. With recent advances in TFP, it is possible to resolve fringe orders upto twelve. The main advantage of this technique is that it requires only a single image for isochromatic demodulation, which makes it suitable especially for problems where recording multiple images is difficult. The accuracy of isochromatic data obtained using TFP/RGB Photoelasticity is dependent on the scanning scheme used to refine the data, which is necessary to incorporate fringe order continuity. In this paper, the existing scanning schemes are critically evaluated for their ability to scan the entire model domain, influence of seed point selection and noise propagation. The scanning schemes are assessed using four problems of increasing level of geometric complexity – Circular disc under compression (simply connected), bi-axially loaded cruciform specimen with an inclined crack, a thick ring subjected to internal pressure and a finite plate with a hole (multiply connected).
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digital Photoelasticity of glass a comprehensive review
Optics and Lasers in Engineering, 2016Co-Authors: K Ramesh, Vivek RamakrishnanAbstract:Abstract The recent advances in digital Photoelasticity have made it possible to use it conveniently for the stress analysis of articles and components made of glass. Depending on the application, the retardation levels to be measured range from a few nanometres to several thousand nanometres, which necessitates different techniques and associated equipments. This paper reviews the recent advances in the Photoelasticity of glass with a focus on the techniques/methods developed in the last decade. A brief introduction to the residual stress in glass is provided initially to bring out its tensorial nature. The subsequent sections are organised thematically rather than chronologically, for better readability and easy access of information.
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a novel method for the evaluation of stress optic coefficient of commercial float glass
Measurement, 2016Co-Authors: Vivek Ramakrishnan, K RameshAbstract:Abstract The measurement of residual stress in float glass is important in glass industries as they affect their cutting quality. Photoelasticity can be used for residual stress analysis of float glass as they exhibit stress induced birefringence. Stress measurement using Photoelasticity necessitates the knowledge of the stress-optic coefficient of float glass. Carrier fringe method in conjunction with digital Photoelasticity is used for the photoelastic calibration of float glass. The conventional method of photoelastic calibration is improved to calibrate float glass with residual stress which eliminates the need for annealing them. The new method developed is self consistent as the results are verified by the reconstruction of the composite fringe pattern. The use of the improved method is recommended for calibration of float glass as it takes into account the residual stress in glass sample apart from its potential for automation.